Spintronics is an emerging technology exploiting both the intrinsic spin of the electron and its associated magnetic moment, in addition to its fundamental electronic charge, in solid-state devices. Spintronics differs from the older magnetoelectronics, in that the spins are not only manipulated by magnetic fields, but also by electrical fields. Spintronics emerged from discoveries in the 1980s concerning spin-dependent electron transport phenomena in solid-state devices.
The Application of Spintronics article tells that the discovery and application by IBM researcher Stuart Parkin and his colleagues of a “spin valve”—essentially the capability to alter the magnetic state of materials at the atomic level—changed the landscape of magnetic data storage by dramatically increasing storage capacity. The first use of spin-valve sensors in hard disk drive read heads was in the IBM Deskstar 16GP Titan, which was released in 1997 with 16.8 GB of storage. Today, the Hitachi Deskstar 7K3000 provides up to 3 TB of storage.
Spintronics is also used to implement memory: MRAM being one of the technologies utilizing spin. Everspin, Freescale, Honeywell, IBM, Infineon, Micron, and Toshiba, as well as start-ups and university research groups—are busy investigating MRAM technology. Spintronics Memory article says that the plan is that future MRAM chips could combine all the advantages of existing memories with none of their shortcomings.
Spintronic Memories to Revolutionize Data Storage article says that superdense MRAM chips based on the bizarre property of electron spin could replace all other forms of data storage. As we build transistors and other components with nanoscale dimensions, we’re fast approaching the point when moving charge is not going to be enough to keep Moore’s Law chugging along. Spin is a fundamental yet elusive quantum attribute of electrons and other subatomic particles. It is often regarded as a bizarre form of nanoworld angular momentum, and it underlies permanent magnetism. What makes spin interesting for electronics is that it can assume one of two states relative to a magnetic field, typically referred to as up and down, and you can use these two states to represent the two values of binary logic—to store a bit, in other words. In principle, manipulating spin is faster and requires far less energy than pushing charge around, and it can take place at smaller scales. We’re still decades away from being able to build spin transistors, but chips that exploit spin in a more modest way are already available. At least one company, Everspin Technologies, of Chandler, Ariz., is now selling magnetoresistive random access memory, or MRAM, a kind of spintronic memory. And many others—including Freescale, Honeywell, IBM, Infineon, Micron, and Toshiba, as well as start-ups and university research groups—are busy investigating MRAM technology. In a tiny region of that material, spin up means 0, and spin down means 1. Proponents say that as MRAM improves, it could combine all the advantages of SRAM, DRAM, flash, and hard disks—with none of their shortcomings. It would be a compact, speedy, low-power, and nonvolatile “universal memory.”
Converting Charge into Spin for Spintronics article tells that encoding bits using the spin of electrons, instead of the usual charge, promises to allow even smaller circuits—but the known processes of flipping electrons’ spins with external magnetic fields are inefficient and require very low temperatures, making such “spintronic” devices impractical. Now, a team of researchers from Germany, the UK, the Czech Republic, and Japan have found a way to manipulate the spin of electrons using electric fields instead of magnetic ones. Their method, reported in the August issue of Nature Materials, could drastically reduce computers’ energy consumption and lessen heat problems caused by miniaturization. Flipping the spin to change a bit requires much less energy than moving charge. You need an effective way to convert charge into spin current in one part of the circuitry that can then be converted again into electric signals in another part.
To be fail on this new MRAM technology compare it also to other storage alternatives shown in Top 10 Candidates for Next-Gen Storage to make your own judgement.
Tomi Engdahl says:
The Zen of Spin
If you took undergraduate quantum mechanics, at some point you were introduced to the concept of “spin.” If you’re like me, you left that class feeling you were shown a magic trick but not how it worked. Don’t worry; you are not alone. The reason you weren’t told more is not that a better explanation was left for graduate quantum mechanics. You weren’t told more because there isn’t a lot more to know.
Of course, there is the magnetic dipole moment. Shoot a beam of electrons through a magnetic field with a gradient, and the beam will bend thanks to the influence of the field on a moving charge. Furthermore, it will also split into two sub-beams — one containing “spin-up” electrons and the other containing “spin-down” electrons. An oriented magnetic dipole moment in the macro world corresponds to circulating current. Hence, the image of a spinning electron, presumably with a non-uniformly distributed charge that gives rise to the magnetic moment.
But if you do the math with some sort of estimate of electron size, the charge has to be spinning at many times the speed of light, which is not possible. Actually, it’s not clear the electron actually has a size, so what is spinning anyway? Not that the spin isn’t real — you can induce electron spin transitions in an atom with polarized light, and photon spin (circular polarization) is real. But the intuitive explanation for the dipole moment is completely wrong, and we still don’t have any concept of just what is spinning.
Tomi Engdahl says:
3D Magnet Stack Subs for Transistors
Germany has discovered new type of magnetic gates
Remember those magnetic core memories that IBM invented at the beginning of the computer revolution. Well now Germany researchers at Technische Universität (Institute for Technical Electronics, TUM; Munich, Germany) have resurrected an analog of the idea using tiny stacks of nanomagnets to write, store, and readout bits.
The researchers also contend that their 3D magnetic transistor-substitutes could be fabricated into any type of gate on standard complementary metal oxide semiconductor (CMOS) lines and are currently inventing magnetic logic techniques that could substitute for CMOS logic and memory functions.
“The material, that can be used is a cobalt/platinum or a cobalt/nickel in a multilayer stack. There are two things that we make sure of: that the material must possesses perpendicular magnetic anisotropy to get a bistable magnetization state of the magnets, and that the anisotropy must be tunable by focused ion-beam irradiation. A cobalt/platinum or a cobalt/nickel multilayer stack fulfills both criteria,”
Tomi Engdahl says:
Future MRAM memory technology: rapid as the main memory, but works as a mass memory
TDK has introduced a prototype of the MRAM memory chips Japanese-held in Chiba, CEATEC trade show. In the memory chips have been read and wrote data about seven times more flash memory faster.
MRAM memory is expected to be replaced to run flash-memory. Its advantages are the dram memory level will reach read and write speeds, but unlike the ram memory, data is retained even after power off.
Although MRAM memory is not actually a new invention, TDK’s presentation of the circuits based on a newer version of stt technology (spin-tansfer torque).
TDK’s rival STT-MRAM circuits development is an American Ever Spin Technologies, whose chips are already used in small amounts, for example, a memory in Buffalo manufactured SSD drives for caching.
Tomi Engdahl says:
Graphene Spintronics Beats All
Moore’s Law to be extended again
Moore’s law may be extended by graphene, whose very high electron mobility plus better-than-metal uniformity makes it a perfect candidate for nanoscale spintronic devices. Spintronic devices encode information on the spin of individual electrons instead of the charge of thousands, which can potentially shrink device sizes into smaller, less power-consuming circuitry than silicon, according to Chalmers University of Technology (U.K.) at its Nanofabrication Laboratory.
Today a few devices use spin encoding, including advanced hard drives and magnetic random access memory (MRAM), but these devices only have to move spin-encoded electrons a few nanometers. Unfortunately, copper and aluminum are not uniform enough to encode spin much longer runs, limiting spintronics capabilities. Chalmers University of Technology’s goal is to extend that distance to millimeters so that any digital circuit can use spintronics.